SCR catalytic converters are the state of the art for removing nitrogen oxide from waste gases. They contribute substantially to reducing ground-level ozone, acid rain and the greenhouse effect. This technology is used in thermal power plants and waste incineration plants, and also in internal combustion engines and in many commercial industries.
In addition to reducing nitrogen oxides, catalytic converters are also used for breaking down dioxins and furans, for example, which has become the recognized industrial standard, particularly in waste incineration plants.
Catalytic converter elements are available, for example, in the form of homogeneously extruded honeycomb elements or in the form of carrier materials, the surface of which is provided with a catalytic layer and which are referred to as plate-type catalytic converters. Additional variants include pellet-type catalytic converters, zeolite catalytic converters, in which the active layer is applied to a ceramic carrier by means of a washcoat process, and catalytic converters designed as corrugated plates.
For installation in SCR reactors, the individual catalytic converter elements are packed into catalytic converter modules (for example, steel modules), which are referred to in the assembly as a catalytic layer. Between the individual catalytic converter modules and between the catalytic converter modules and the wall of the reactor housing that holds the modules, seals are provided, which are designed to forcefully guide the flow of waste gas through the catalytic converter elements.
The pressure loss that is associated with installing the catalytic converter modules into the reactor is considered a critical performance parameter. Efforts are made to minimize this undesirable pressure loss. The pressure loss is influenced by the selected geometry of the catalytic converter elements, among other factors. However, the selected geometry is subject to production-based and process-based limits. The size of the SCR reactor likewise has a direct impact on the pressure loss. Thus leeway in terms of configuration is subject to certain limits: on one hand from on-site restrictions, particularly in the case of retrofitted SCR reactors, and on the other hand from economic considerations.